Leases (Schedule of Cumulative Effects of Adoption of ASC 842) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 173,739	$ 215,233		$ 197,755	$ 160,593	$ 154,744		$ 183,727
Accounts receivable, net	224,232			223,176
Contract assets	64,571			57,447
Inventories	105,705			85,904
Income taxes prepaid and receivable	6,774			7,473
Prepaid expenses and other current assets	24,849			21,294
Total current assets	599,870			593,049
Property, plant and equipment, net	449,299			462,055
Intangibles, net	44,530			49,206
Goodwill	162,075			164,382
Deferred income taxes	51,761			62,622
Noncurrent receivables	45,699			45,061
Other assets	51,488			41,617
Total assets	1,404,722			1,417,992
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable
Accounts payable	60,994			52,246
Accrued liabilities	122,741			129,030
Current maturities of long-term debt	20			1,224
Income taxes payable	7,787			6,806
Total current liabilities	191,542			189,306
Long-term debt	424,012			523,707
Other noncurrent liabilities	118,153			88,277
Deferred taxes and other liabilities	7,934			8,422
Total liabilities	741,641			809,712
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital	431,860			430,555
Retained earnings	675,491			589,645
Accumulated items of other comprehensive income:
Translation adjustments	(139,153)			(115,976)
Pension and postretirement liability adjustments	(48,146)			(47,109)
Derivative valuation adjustment	(4,172)			4,697
Treasury stock (Class A), at cost 8,418,620 shares in 2018 and 8,431,335 shares in 2017	(256,391)			(256,603)
Total Company shareholders' equity	659,530			605,249
Noncontrolling interest	3,551			3,031
Total equity	663,081	651,316	$ 626,407	608,280	605,134	588,630	$ 592,578	573,015
Total liabilities and shareholders' equity	1,404,722			1,417,992
Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock	39			37
Accumulated items of other comprehensive income:
Total equity	39	39	37	37	37	37	37	37
Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock	2			3
Accumulated items of other comprehensive income:
Total equity	$ 2	$ 2	$ 3	3	$ 3	$ 3	$ 3	$ 3
Accounting Standards Update 2018-11 [Member] | Adjustments Increase/(Decrease) [Member]
Assets
Cash and cash equivalents
Accounts receivable, net
Contract assets
Inventories
Income taxes prepaid and receivable
Prepaid expenses and other current assets				(370)
Total current assets				(370)
Property, plant and equipment, net				(6,144)
Intangibles, net
Goodwill
Deferred income taxes				(20)
Noncurrent receivables
Other assets				13,615
Total assets				7,081
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable
Accounts payable
Accrued liabilities				4,964
Current maturities of long-term debt				(1,206)
Income taxes payable
Total current liabilities				3,758
Long-term debt				(24,680)
Other noncurrent liabilities				27,968
Deferred taxes and other liabilities
Total liabilities				7,046
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital
Retained earnings				35
Accumulated items of other comprehensive income:
Translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Treasury stock (Class A), at cost 8,418,620 shares in 2018 and 8,431,335 shares in 2017
Total Company shareholders' equity				35
Noncontrolling interest
Total equity				35
Total liabilities and shareholders' equity				7,081
Accounting Standards Update 2018-11 [Member] | Adjustments Increase/(Decrease) [Member] | Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock
Accounting Standards Update 2018-11 [Member] | Adjustments Increase/(Decrease) [Member] | Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock
Accounting Standards Update 2018-11 [Member] | Opening balance, as adjusted [Member]
Assets
Cash and cash equivalents				197,755
Accounts receivable, net				223,176
Contract assets				57,447
Inventories				85,904
Income taxes prepaid and receivable				7,473
Prepaid expenses and other current assets				20,924
Total current assets				592,679
Property, plant and equipment, net				455,911
Intangibles, net				49,206
Goodwill				164,382
Deferred income taxes				62,602
Noncurrent receivables				45,061
Other assets				55,232
Total assets				1,425,073
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable
Accounts payable				52,246
Accrued liabilities				133,994
Current maturities of long-term debt				18
Income taxes payable				6,806
Total current liabilities				193,064
Long-term debt				499,027
Other noncurrent liabilities				116,245
Deferred taxes and other liabilities				8,422
Total liabilities				816,758
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital				430,555
Retained earnings				589,680
Accumulated items of other comprehensive income:
Translation adjustments				(115,976)
Pension and postretirement liability adjustments				(47,109)
Derivative valuation adjustment				4,697
Treasury stock (Class A), at cost 8,418,620 shares in 2018 and 8,431,335 shares in 2017				(256,603)
Total Company shareholders' equity				605,284
Noncontrolling interest				3,031
Total equity				608,315
Total liabilities and shareholders' equity				1,425,073
Accounting Standards Update 2018-11 [Member] | Opening balance, as adjusted [Member] | Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock				37
Accounting Standards Update 2018-11 [Member] | Opening balance, as adjusted [Member] | Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock				$ 3